Seismic surveying can be applied to the search and evaluation of subterranean hydrocarbons. One type of seismic survey is generally referred to as a towed marine survey, and includes a manned vessel towing a series of seismic streamers (containing seismic sensors) behind the vessel, and creating an impulse that travels through the water and into the formation, where the impulse reflects and reverberates back to the streamers through the water. The signals are detected and recorded by the sensors, and data is produced. This data can be analyzed and processed to provide information (often images) to represent aspects of the formation such as presence of minerals such as hydrocarbons, or lack thereof.
Land surveys are different from marine surveys in that they occur on “dry” land (or shallow water such as swamps or wetland). Large numbers of sensors are placed on or in the ground, an impulse is provided into the ground and reflects and reverberates against the formation, and the sensors detect the signals. The detected signals are recorded as data that can be analyzed and processed to provide information (often images) to represent aspects of the formation such as presence of minerals such as hydrocarbons, or lack thereof.
Towed marine surveys are not suitable for every marine survey situation. Thus, seabed surveys can be used. In seabed surveys the principals of the sensors and the impulse are similar, but sensors are placed directly on, into, or very close to the seabed. The sensors can be in the form of nodes (similar to land) or as cables containing sensors (similar to those used in marine surveys), or a combination thereof.
Deployment and retrieval of the sensors for seabed surveys in such a way as to be useful and efficient enough to allow for a technically and commercially successful survey is difficult.
The present application provides a number of combined features to address unmet needs in those areas.